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// See the LICENSE file in the project root for more information
// 
// Licensed to the Apache Software Foundation (ASF) under one or more
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// this work for additional information regarding copyright ownership.
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
// 
// http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// 

using System;

namespace log4net.Core
{
    /// <summary>
    /// An evaluator that triggers on an Exception type
    /// </summary>
    /// <remarks>
    /// <para>
    /// This evaluator will trigger if the type of the Exception
    /// passed to <see cref="M:IsTriggeringEvent(LoggingEvent)"/>
    /// is equal to a Type in <see cref="ExceptionType"/>.    /// 
    /// </para>
    /// </remarks>
    /// <author>Drew Schaeffer</author>
    public class ExceptionEvaluator : ITriggeringEventEvaluator
    {
        /// <summary>
        /// The type that causes the trigger to fire.
        /// </summary>
        private Type m_type;

        /// <summary>
        /// Causes subclasses of <see cref="ExceptionType"/> to cause the trigger to fire.
        /// </summary>
        private bool m_triggerOnSubclass;

        /// <summary>
        /// Default ctor to allow dynamic creation through a configurator.
        /// </summary>
        public ExceptionEvaluator()
        {
            // empty
        }

        /// <summary>
        /// Constructs an evaluator and initializes to trigger on <paramref name="exType"/>
        /// </summary>
        /// <param name="exType">the type that triggers this evaluator.</param>
        /// <param name="triggerOnSubClass">If true, this evaluator will trigger on subclasses of <see cref="ExceptionType"/>.</param>
        public ExceptionEvaluator(Type exType, bool triggerOnSubClass)
        {
            if (exType == null)
            {
                throw new ArgumentNullException("exType");
            }

            this.m_type = exType;
            this.m_triggerOnSubclass = triggerOnSubClass;
        }

        /// <summary>
        /// The type that triggers this evaluator.
        /// </summary>
        public Type ExceptionType
        {
            get { return this.m_type; }
            set { this.m_type = value; }
        }

        /// <summary>
        /// If true, this evaluator will trigger on subclasses of <see cref="ExceptionType"/>.
        /// </summary>
        public bool TriggerOnSubclass
        {
            get { return this.m_triggerOnSubclass; }
            set { this.m_triggerOnSubclass = value; }
        }

        /// <summary>
        /// Is this <paramref name="loggingEvent"/> the triggering event?
        /// </summary>
        /// <param name="loggingEvent">The event to check</param>
        /// <returns>This method returns <c>true</c>, if the logging event Exception 
        /// Type is <see cref="ExceptionType"/>. 
        /// Otherwise it returns <c>false</c></returns>
        /// <remarks>
        /// <para>
        /// This evaluator will trigger if the Exception Type of the event
        /// passed to <see cref="M:IsTriggeringEvent(LoggingEvent)"/>
        /// is <see cref="ExceptionType"/>.
        /// </para>
        /// </remarks>
        public bool IsTriggeringEvent(LoggingEvent loggingEvent)
        {
            if (loggingEvent == null)
            {
                throw new ArgumentNullException("loggingEvent");
            }

            if (this.m_triggerOnSubclass && loggingEvent.ExceptionObject != null)
            {
                // check if loggingEvent.ExceptionObject is of type ExceptionType or subclass of ExceptionType
                Type exceptionObjectType = loggingEvent.ExceptionObject.GetType();
                return exceptionObjectType == this.m_type || this.m_type.IsAssignableFrom(exceptionObjectType);
            }
            else if (!this.m_triggerOnSubclass && loggingEvent.ExceptionObject != null)
            {   // check if loggingEvent.ExceptionObject is of type ExceptionType
                return loggingEvent.ExceptionObject.GetType() == this.m_type;
            }
            else
            {   // loggingEvent.ExceptionObject is null
                return false;
            }
        }
    }
}
